Acne is a disease that affects the oil-producing glands (sebaceous glands) in the skin. The oil these glands make is called sebum. Sebaceous glands produce very little sebum before puberty, but during puberty, they start to make larger quantities due to an increase in hormones that follows puberty. Sebum normally flows up to the skin surface through hair follicles. Acne occurs when the path of sebum is blocked, usually by dead skin cells mixed with sebum. The hormones that have the greatest effect on the sebaceous glands are the male hormones called androgens. Both women and men carry male hormones, of course, in different quantities.